Accelerating Li desolvation via symmetry-broken engineering of iron single-atom catalysts for high-performance lithium-sulfur batteries.

High-energy-density lithium-sulfur (Li-S) batteries are hindered by the detrimental shuttle effect and sluggish redox conversion kinetics of lithium polysulfides (LiPSs) arising from the high energy barrier of Li diffusion kinetics at the electrode/electrolyte interface. Herein, the asymmetrically N,S co-coordinated atomic Fe sites (FeSAC-NS) are synthesized to present a strong interaction with Li based on the typical symmetry-broken electron redistribution. Comprehensive electrochemical and theoretical results reveal that FeSAC-NS as an efficient Li power pump could kinetically accelerate the dissociation of Li solvation structure and enhance the Li diffusion kinetics via the N-Fe-S active structure, further improving the bidirectional sulfur species redox electrochemistry. Encouraged by the FeSAC-NS catalytic promoter, the constructed Li-S batteries delivered an exceptional rate performance of 767 mAh g at 5 C and a high cyclic stability of 0.034% decaying rate over 700 cycles at 1 C. Even at a low temperature of 0 °C, the FeSAC-NS-based cells exhibited a low decay rate of 0.056% per cycle over 350 cycles at 0.5 C. This work provides a deep insight into the underlying mechanism of Li desolvation behavior facilitated by symmetry-broken atomic Fe sites.